1. Field of the Invention
This invention generally relates to geometrical instruments and, more particularly, to adjustable instruments for making combined linear and angular measurements.
2. Description of the Prior Art
A number of adjustable layout tools have been developed which allow varying degrees of flexibility in making combined linear and angular measurements. For purposes of illustration, patents representative of such devices include U.S. Pat. No. 652,814 (Setzer); U.S. Pat. No. 2,435,529 (Brockley); U.S. Pat. No. 2,571,569 (Greenwood); U.S. Pat. No. 2,822,834 (Hammers); and U.S. Pat. No. 3,269,015 (Barker); although this listing is not represented to be, nor intended to be, in any way exhaustive. A number of layout tools have also been developed in which several components have been detachably joined, thus allowing use of the components separately as individual tools. Although the prior art devices do provide for relating a linear measurement to an angular measurement, the utility of even the most versatile devices is limited by disadvantages which restrict the range of combined measurements that can be made conveniently. The Barker instrument referred to above, for example, in which two tape measures are mounted on the ends of two arms which are rotatably joined at their other ends permits linear and angular measurements from a vertex which is located at the intersection point of the center lines of the arms provided that the angular measurements do not fall within the area of overlap of the two arms.